JPH05186724A - Ink for ink jet printer and its preparation - Google Patents

Abstract

PURPOSE:To provide the title ink which can prevent the agglomeration of a pigment in an ink and can insure ink delivery stability and shelf stability and to provide a method for the preparation thereof. CONSTITUTION:An ink composition comprising a pigment dispersed in a dispersion medium comprising a nonpolar insulating solvent, which ins produced by a process comprising the first step comprising a granulating step for adjusting the diameter of dispersed particles of the pigment and the second step for imparting dispersion stability to the pigment dispersed in the solvent. In the first step, the pigment is dispersed to have a primary particle diameter and then re-agglomerated to have a desired particle diameter by the action of a specified resin. After the diameter of the dispersed pigment particle is adjusted to a desired valve, a resin or a dispersion stabilizer is added to stabilize the dispersed pigment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink used in an ink jet recording apparatus for ejecting ink to form characters and images on a transfer medium such as recording paper, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, ink jet recording methods can be roughly classified into two types, a continuous type and an on-demand type. As an ink used in such an inkjet system, an ink in which a dye is dissolved in water is predominant (hereinafter referred to as an aqueous ink).

However, the water-based ink has a problem that the print quality greatly depends on the paper type, from the one which can obtain a good print quality depending on the quality of the transferred paper to the one which shows a very bad print quality. ing.

In recent years, various inks in which fine pigment particles are dispersed in an aqueous dispersion medium or a non-aqueous dispersion medium have been reported as inks for ink jet printers which solve the above problems. For example, Japanese Patent Publication No. 61-55547 discloses a recording liquid in which a pigment is dispersed in a liquid medium using a dispersant, and a method for producing the recording liquid.

The advantages of the ink jet recording method using these inks are that the recording is direct recording, the process is simple, there is no noise, and high-resolution recording is possible because minute ink droplets are ejected. It has excellent characteristics and its future is drawing attention.

[0006]

However, the ink in which the pigment is dispersed in the aqueous dispersion medium or the non-aqueous dispersion medium has a problem when the conventional water-soluble dye is dissolved in the water-soluble medium (print quality paper). However, due to the poor dispersion stability of the pigment in the water-soluble dispersion medium or the non-water-soluble dispersion medium, agglomeration between pigment particles occurs and clogging of the nozzle portion of the ink ejection head occurs. However, there is a problem in that the ink cannot be used because the viscosity changes and the viscosity exceeds the ink ejection limit viscosity range.

Therefore, the present invention is to solve these problems, and an object of the present invention is to provide an ink for an ink jet printer capable of suppressing aggregation of pigment in the ink and ensuring ink ejection stability and storage stability. It is to provide a manufacturing method.

[0008]

In the ink for an inkjet printer of the present invention, the dispersion medium is a non-polar insulating solvent, and in the ink composition in which the pigment is dispersed in the dispersion medium, the pigment of the pigment is used as the first step. It is characterized in that it has a granulation step of adjusting the dispersed particle diameter, and thereafter, as a second step, it is produced from two steps of imparting dispersion stability to the dispersed pigment in the non-polar insulating solvent.

In the method for producing an ink for an ink jet printer of the present invention, the dispersion medium is a non-polar insulating solvent, and in the ink composition in which the pigment is dispersed in the dispersion medium, the dispersed particle size of the pigment is used as the first step. It is characterized by comprising a granulation step of adjusting the above, and then, as a second step, it is produced from two steps of imparting dispersion stability to the non-polar insulating solvent to the dispersed pigment.

The ink for an ink jet printer of the present invention has a step of dispersing the pigment to a primary particle diameter in the first granulation step and then reaggregating the pigment to a desired particle diameter by the action of a specific resin. Characterize.

The ink for an ink jet printer of the present invention is characterized by including a step of stabilizing the dispersed pigment by adding a resin or a dispersion stabilizer after adjusting the dispersed particle diameter of the pigment to a desired particle diameter.

The ink-jet printer ink of the present invention is characterized in that the resin is composed of a portion which is solvated with a nonpolar insulating solvent, a portion which is difficult to be solvated and a portion having a polar group.

In the ink for an ink jet printer of the present invention, the resin is a copolymer resin, and the monomer constituting the solvation part in the non-polar insulating solvent is lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, cetyl. The monomer that is composed of methacrylate and constitutes the part that is difficult to solvate is methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, styrene, vinyltoluene, and the polar group-containing monomer is acrylic acid, methacrylic acid, itaconic acid, and fumaric acid. Acid, maleic acid, styrene sulfonic acid, dimethylaminomethyl methacrylate, diethylaminoethyl methacrylate, vinyl pyridine, vinyl pyrrolidone, vinyl pepyridine,
Characterized by selecting from vinyl lactams.

The method for producing an ink for an ink jet printer of the present invention is characterized in that the resin or dispersion stabilizer is added after the pigment is added to the solvent in which the resin has been synthesized in advance to adjust the particle size of the dispersed pigment.

[0015]

EXAMPLES Examples of the present invention will be described in detail below.

The manufacturing process of the present invention includes the steps 1 and 2 of step 2.
It consists of two processes.

Step 1 is a step of adjusting the particle size of the dispersed pigment. To illustrate one processing method of this step, the pigment is added to the solution A in which the resin is previously copolymerized in a nonpolar insulating solvent. After the primary particles are dispersed, the dispersion share is changed to adjust the dispersed pigment to a desired dispersed particle size (the primary particles of the pigment are re-aggregated by the action of a specific resin) to obtain a dispersion B. At this time, the share of the selected copolymer resin and dispersion is a major factor in determining the particle size of the pigment.

Step 2 is a solution C (a resin or a dispersion stabilizer in a nonpolar insulating solvent, which is a solution of a resin or a dispersion stabilizer having a dispersing effect on the pigment particles in the dispersion B obtained in the above Step 1). Is added and dissolved) to stabilize the dispersion for a certain period of time.

As the ink for the ink jet printer of the present invention, the ink viscosity when the temperature during operation of the printing apparatus is set to 0 to 50 ° C., the ink droplet formation stability and flight stability under high speed response of the head. From the viewpoint of the property, it is necessary to be 30 mPa · s or less in the vicinity of the nozzle at the time of ejection, and 1.0 to 15 mPa · s is more preferable in order to realize even faster response.

The following may be considered as the composition in the ink of the present invention.

Colorants that can be used in the present invention include pigments. The pigment that can be used in the present invention is not particularly limited, and for example, for black and white, furnace black, lamp black, acetylene black, carbon black such as channel black, or copper, iron,
Examples thereof include metals such as titanium oxide or metal oxides, and organic pigments such as ortho-nitroaniline black. For color, toluidine red, permanent carmine FB, fast yellow AAA, disazo orange P
MP, lake red C, brilliant carmine 6B, phthalocyanine blue, quinacridone red, dioxane violet, pictoria pure blue, alkali blue toner, first yellow 10G, disazo yellow AAMX, disazo yellow AAOT, disazo yellow A
AOA, yellow iron oxide, disazo yellow HR, orthonitroaniline orange, dinitroaniline orange, vulcan orange, toluidine red, chlorinated para red,
Brilliant Fast Scarlet, Naphthol Red 23, Pyrazolone Red, Barium Red 2B, Calcium Red 2B, Strontium Red 2B, Manganese Red 2B, Barium Lisome Red, Pigment Scar Red 3B Lake, Lake Bordeaux 10B, Anthocin 3B Lake, Anthocin 5B Rake, Rhodamine 6
G Lake, Eosin Lake, Bengara, Fafthor Red FGR, Rhodamine B Lake, Methyl Bio Red Lake, Dioxazine Bio Red, Basic Blue 5B Lake, Basic Blue 6G Lake, Fast Sky Blue, Alkaline Blue R Toner, Peacock Blue Lake, Navy blue, ultramarine, reflex blue 2G, reflex blue R, brilliant green lake, diamond green thioflavin lake, phthalocyanine green G, green gold, phthalocyanine green Y, iron oxide powder, rust, zinc white, titanium oxide, calcium carbonate , Clay, barium sulfate, alumina white,
Aluminum powder, bronze powder, daylight fluorescent pigment, pearl pigment, naphthol carmine FB, naphthol red M,
Permanent carmine FB, Fastello G, Disazo Yellow AAA, Disazo Orange PMP, Lake Red C, Dioxane Bio Red, Alkali Blue G toner and the like, and other processed pigments such as graft carbon having the pigment surface treated with a resin or the like can be used. The addition amount is 1 to 3.
0 polymerization% is preferable, and 3-12 polymerization% is more preferable. A pigment having a particle size of 25 μm or less is used, and a pigment having particles of 5 μm or less is preferably used.

Further, the ink for an ink jet printer of the present invention contains a resin and / or a dispersion for the purpose of adjusting the particle size of the dispersed pigment and adjusting the viscosity of the ink, or improving the scratch resistance of the recorded matter after printing and recording. Add stabilizer.

Specifically, the resin used in the present invention can be obtained by copolymerizing monomers. As an example, it is preferable to have a part that solvates with a nonpolar insulating solvent and a part that does not solvate with a nonpolar insulating solvent, and to have a polar group that bonds both parts.

For example, as a monomer which is solvated after polymerization in a nonpolar insulating solvent, lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, cetyl methacrylate and the like can be mentioned. Also,
Examples of the monomer that is difficult to be solvated after polymerization in a nonpolar insulating solvent include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, styrene, and vinyltoluene.

As the monomer having a polar group used as a reaction active point for copolymerizing the easily solvable portion and the poorly solvable portion, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, styrene are used. Examples include sulfanic acid, dimethylaminomethyl methacrylate, diethylaminoethyl methacrylate, vinylpyrrolidone, vinylpyridine, vinylpiperidine, vinyllactam and the like.

In the present invention, the selection of resin is pigment particle size,
From the viewpoint of the viscosity and the durability of the printed matter after printing, the polymerization ratio and the molecular weight of the above monomers are determined. In addition to the above examples, rosin-modified resin, styrene-butadiene resin, vinyltoluene-acrylic copolymer and the like can be used.

In the present invention, as the second step, a dispersion stabilizer is added for the purpose of maintaining the dispersion stability of the dispersed pigment. As the dispersion stabilizer, an ionic (anionic or cationic), amphoteric or nonionic surfactant, or a fluorine-based, silicon-based or polymer-based surfactant or a polymer compound can be added. Examples of the anionic surfactant include higher fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfate ester salts, higher alkyl sulfonates, condensates of higher fatty acids and amino acids, sulfosuccinate ester salts, naphthenates, etc. .. Examples of the cationic surfactant include an aliphatic amine salt, a quaternary ammonium salt, a sulfonium salt, and a phosphonium salt. Specific examples thereof include octadecylamine acetate, alkyltrimethylammonium chloride, polyoxyethylene octadecylamine, and polyoxyethylene alkyl. Examples include amines and polymeric amines.

The amphoteric surfactant is a betaine type such as dimethylalkyl betaine. As the nonionic surfactant, fatty acid ester type of polyoxyethylene compound, polyethylene oxide condensation type and the like can be used.

In addition to the above, a resin obtained by copolymerizing the above-mentioned monomers can also be used.

As the non-polar insulating solvent which can be used in the present invention, an aliphatic hydrocarbon solvent, specifically, Isopar of Exxon Co., Soltor of Philippe Petroleum Co., IP Solvent of Idemitsu Petrochemical Co., or Shell of petroleum naphtha is used. Petrochemical S. B. R. , Shelsol, Vegasol of Mobil Oil Co., and the like. The properties required for the nonpolar insulating solvent of the present invention are low toxicity, low flammability, and low odor. These may be used in combination of two or more depending on the case.

The ink for an ink jet printer of the present invention and the method for producing the same using the above-described ink composition will be described step by step.

Example 1 Ink composition Dispersion pigment (coloring material) type Carbon black MA-100 (manufactured by Mitsubishi Kasei) 20 parts by weight Resin stearyl methacrylate-acrylic acid copolymer 27.5 parts by weight Dispersion stabilizer sorbitan trioleate 2 Parts by weight Dispersion medium Isopar L (manufactured by Exxon Petrochemical Co., Ltd.) 450.5 parts by weight Step 1 Solution A is formulated as follows. 10 parts by weight of commercially available stearyl methacrylate, 6 parts by weight of acrylic acid and 6.0 parts by weight of vinyl pepyridine were added to 350.5 parts by weight of Expar L manufactured by Exxon Petrochemical Co., Ltd. A copolymer resin solution of stearyl methacrylate and acrylic acid having an average molecular weight (weight basis) of 16000 was obtained.

Next, 20 parts by weight of MA-100 manufactured by Mitsubishi Kasei Co., Ltd. was added to the solution A obtained in the above step, and the solution A was thoroughly permeated into carbon black, and then an ultrasonic disperser (Nippon Seiki Co., Ltd.) was used. Disperse carbon black up to the primary particle size with the manufactured model RUS-300). Next, the above-mentioned dispersion liquid is circulated horizontally placed type mill M100 (EIGER ENGINEE
RING LIMITED bead mill) 0.9 mm beads were dispersed at 5000 rpm for 1 hour to obtain a dispersion B having an average particle diameter of the pigment of 2 μm.

Step 2 Solution C was formulated as follows. To 100 parts by weight of Isopar L, 2.5 parts by weight of stearyl methacrylate, 1.5 parts by weight of acrylic acid and 1.5 parts by weight of vinyl pepyridine were added, and the mixture was stirred overnight while heating at 60 ° C. to have an average molecular weight (weight basis) of 16000. To obtain a copolymer resin solution of stearyl methacrylate and acrylic acid. Then, 2 parts by weight of sorbitan trioleate was added and dissolved to obtain a solution C.

Next, the dispersion B obtained in the step 1 is stirred.
While stirring with HI-15 (Tokyo Rikiki Co., Ltd.), Solution C was gradually added to completely adsorb the copolymer resin of stearyl methacrylate and acrylic acid in Solution C to the dispersion pigment.

By the steps 1 and 2 described above, the ink for an ink jet printer of Example 1 of the present invention is obtained.

Example 2 Ink composition Dispersion pigment (coloring material) Carbon black MA-100 (manufactured by Mitsubishi Kasei) 30 parts by weight Solution A Dissolving resin Lauryl methacrylate-styrene copolymer resin Monomer (solvating part) Lauryl methacrylate 15 Parts by weight Monomer (part which is difficult to be solvated) Styrene 10 parts by weight Reaction active site Dimethylaminomethyl methacrylate 10 parts by weight Solvent Isopar L 250 parts by weight Solution C Dissolved resin Stearyl methacrylate-acrylic acid copolymer resin Monomer (part which is solvated) Stearyl methacrylate 15 parts by weight Monomer (part which is difficult to be solvated) Acrylic acid 25 parts by weight Reaction active site Vinyl pepyridine 6.25 parts by weight Solvent Isopar L 157.5 parts by weight Dispersion stabilizer Not added Example of ink production Same as 1 Step 1 and Step 2
Created in. In Example 2, no dispersion stabilizer was added in step 2.

The average molecular weight (weight average) of the lauryl methacrylate-styrene copolymer resin of solution A was 2300.
0, the average molecular weight (by weight) of the stearyl methacrylate-methacrylic acid copolymer resin of Solution C was 14,000.

Example 3 Ink Composition Dispersion Pigment (Coloring Material) Carbon Black MA-100 (manufactured by Mitsubishi Kasei) 40 parts by weight Solution A Dissolving resin Lauryl methacrylate-styrene copolymer resin Monomer (solvating part) Lauryl methacrylate 40 Parts by weight Monomers (parts that are difficult to solvate) Styrene 11.25 parts by weight Reaction active site Dimethylaminomethyl methacrylate 11.25 parts by weight Solvent Isopar L 300 parts by weight Solution C Dissolved resin Not added Dispersion stabilizer Sorbitan trioleate 4 parts by weight Solvent Isopar L 93.4 parts by weight The method for producing the ink is the same as in Example 1, Step 1 and Step 2.
Created in. In Example 3, no copolymer resin was added in step 2 for the purpose of stabilizing dispersion.

The average molecular weight (weight basis) of the lauryl methacrylate-styrene copolymer resin of solution A is 18,000.
Met.

Example 4 Ink composition Dispersion pigment (coloring material) Carbon black MA-100 (product of Mitsubishi Kasei) 30 parts by weight Solution A Dissolving resin Lauryl methacrylate-styrene copolymer resin Monomer (solvating part) Lauryl methacrylate 15 Parts by weight Monomer (part that is difficult to solvate) Styrene 10 parts by weight Reaction active site Dimethylaminomethyl methacrylate 10 parts by weight Solvent Isopar L 250 parts by weight Solution C Dissolving resin Stearyl methacrylate-methacrylic acid copolymer resin Resin monomer (part to be solvated) Stearyl methacrylate 15 parts by weight Monomer (part that is difficult to solvate) Methacrylic acid 6.25 parts by weight Reaction active site Vinyl pepyridine 6.25 parts by weight Dispersion stabilizer not added Solvent Isopar L 157.5 parts by weight Implementation 1 similar to that of steps 1 and 2
Created in. In Example 4, no dispersion stabilizer was added in step 2.

The average molecular weight (weight average) of the lauryl methacrylate-styrene copolymer resin of solution A is 1800.
0, the average molecular weight (weight average) of the stearyl methacrylate-methacrylic acid copolymer resin of Solution C was 12,000.

Next, an ink for an ink jet printer of a comparative example of the present invention and a method for producing the same will be described.

Comparative Example 1 Ink composition Dispersion pigment (coloring material) Carbon black MA-100 (manufactured by Mitsubishi Kasei) Solution A Dissolving resin Lauryl methacrylate-styrene copolymer resin Monomer (solvating part) Lauryl methacrylate 40 parts by weight Monomer (Part that is difficult to solvate) Styrene 11.25 parts by weight Reaction active site dimethylaminomethyl methacrylate 11.25 parts by weight Solvent Isopar L 407.5 parts by weight The ink of Comparative Example 1 was produced in the same manner as in Example 1. However, step 2 which is a dispersion stabilization step is not performed.

The average molecular weight (weight average) of the lauryl methacrylate-styrene copolymer resin of solution A was 18,000.
Met.

Comparative Example 2 Ink composition Dispersion pigment (coloring material) Carbon black MA-100 (manufactured by Mitsubishi Kasei) Dissolved resin Styrene butadiene resin Dispersion stabilizer Sorbitan trioleate Non-polar insulating solvent Isopar L Comparative example 2 of the present invention Can be produced by known methods. As an example, after adding a dispersion stabilizer and a resin to a non-polar insulating solvent, a pigment is added and treated with a dispersing machine such as a ball mill, an attritor, or a sand mill to prepare a uniform dispersion system for an inkjet printer of a comparative example. Get the ink.

After the ink was prepared by the ink composition and the production method described above, the ink was used for the ink jet printer ink of the present invention and the comparative example ink by evaluating the storage stability of the ink and actually ejecting the ink with an ink jet printer.

Ink storage stability test: The state of aggregation of the dispersed pigment in the ink was confirmed. The ink sealed at a high temperature of 70 ° C. was allowed to stand for 6 months and then observed, and sedimentation was observed but easily redispersed.・ ・ ・ Satisfactory (⊚) ・ Settling is observed but aggregation (hard cake) does not occur.・ ・ ・ (○) Suitable ・ Settling aggregation has occurred. ... Classified and evaluated by unsuitability (x). The results are shown in Table 1.

[0049]

[Table 1]

Next, the ink printing evaluation for the purpose of evaluating the clogging test at the ink ejection portion was carried out by using an ink jet printer head as shown in FIG. FIG. 1 is a sectional view showing an inkjet head structure used in this embodiment. Specifically, it has a structure in which the pressure generating member 2 composed of laminated piezoelectric elements is adhered to the wall surface of the cavity 3. At the time of driving, the pressure generating member 2 is bent by the applied voltage to pressurize the ink in the cavity, whereby the ink is ejected from the nozzle 1. 4 in FIG. 1 in the figure
Is ink, and 5 is an ink droplet ejected from the nozzle 1. The ejection nozzle diameter of this inkjet printer head is 50 μm, the piezoelectric element drive voltage is 50 V, and the drive frequency is 2 k.
Hz, resolution 300 dots / inch.

According to the structure of the ink jet printer head as described above, since the ejection speed is high, the ink transfer area is wide, the number of dots can be reduced, the resolution can be increased, and the margin for the ink physical properties such as viscosity and surface tension can be increased. It has excellent characteristics as an ink jet printer, such as a wide range and is less likely to be clogged.

The following evaluations were carried out using the above inkjet printer head.

Ink clogging test: The head having the structure shown in FIG. 1 was filled with ink, and the nozzle was left in an environment of 40 ° C. without a cap for 2 weeks to evaluate the ink ejection state. Discharge ・ ・ ・ Satisfactory (◎) ・ Rubbing with a rubber plate Discharge ・ ・ ・ Appropriate (○) ・ No discharge ・ ・ ・ Inappropriate (×) The results are shown in Table 1.

The inks for ink jet printers of the present invention all have high ink storage stability in all evaluations carried out this time, and also show good results in a clogging test of ink nozzles. Was preferred. On the other hand, Comparative Examples 1-2
In either of the ink storage stability and the nozzle clogging test, the above ink was unsuitable as an ink for inkjet printers.

From the above, it is confirmed that the ink storage stability is high and the ink ejection head is less likely to be clogged by using the conventional two-step ink production method as well as the conventional dispersion ink. Was done.

Although the embodiments of the present invention have been described in detail above, the ink for an ink jet printer of the present invention is not limited to these constitutions, materials and manufacturing methods.

[0057]

As described above, according to the ink for an ink jet printer of the present invention, there is no clogging of the ink discharge head nozzle, which is a concern of the dispersion type ink which has been a problem in the past, and high ink storage is possible. I was able to achieve stability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method of recording ink for an inkjet printer of the present invention.

[Explanation of symbols]

 1 Nozzle 2 Pressure Generating Member (Layered Piezoelectric Element) 3 Cavity Member 4 Ink 5 Ink Drop

Claims (7)

[Claims] 1. The dispersion medium is a non-polar insulating solvent,
In the ink composition in which the pigment is dispersed in the dispersion medium,
As a first step, there is a granulation step of adjusting the dispersed particle size of the pigment, and then as a second step, two steps of imparting dispersion stability to the dispersed pigment in the non-polar insulating solvent are performed. An ink for an inkjet printer, which is characterized by being manufactured. 2. The dispersion medium is a non-polar insulating solvent,
In the ink composition in which the pigment is dispersed in the dispersion medium,
As a first step, there is a granulation step of adjusting the dispersed particle size of the pigment, and then as a second step, two steps of imparting dispersion stability to the dispersed pigment in the non-polar insulating solvent are performed. A method for producing an ink for an ink jet printer, which comprises producing the ink. 3. The method according to claim 1, further comprising a step of dispersing the pigment to a primary particle diameter in the first granulation step and then reaggregating the pigment to a desired particle diameter by the action of a specific resin. Ink for an inkjet printer as described. 4. The inkjet printer according to claim 1, further comprising the step of stabilizing the dispersed pigment by adding a resin or a dispersion stabilizer after adjusting the dispersed particle diameter of the pigment to a desired particle diameter. Ink. 5. The ink for an ink jet printer according to claim 3, wherein the resin comprises a portion which is solvated with a nonpolar insulating solvent, a portion which is difficult to be solvated and a portion which has a polar group. 6. The resin is a copolymer resin, and the monomer constituting the solvation part in a non-polar insulating solvent is lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, cetyl methacrylate, Monomers that compose the difficult part are methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, styrene, vinyltoluene, and polar group-containing monomers are acrylic acid, methacrylic acid, itaconic acid, fumaric acid,
The ink for an ink jet printer according to claim 5, wherein the ink is selected from maleic acid, styrenesulfonic acid, dimethylaminomethylmethacrylate, diethylaminoethylmethacrylate, vinylpyridine, vinylpyrrolidone, vinylpepyridine, and vinyllactam. 7. The ink for an ink jet printer according to claim 2, wherein the resin or the dispersion stabilizer is added after the pigment is added to the solvent in which the resin is synthesized in advance to adjust the particle size of the dispersed pigment. Production method.